In 2014 treeze Ltd was mandated together with Department for Sustainable Buildings ETH Zurich and Architekturbüro Preisig Pfäffli by the Federal Office of Energy (BfE), the Federal Office of Environment (BAFU), and the Municipal Office for Building Construction of Zurich (AHB) to find target and reference values regarding the total environmental impacts of buildings (download the report of Wyss et al. 2014).

In 2016, treeze Ltd., Architekturbüro Preisig Pfäffli and Sustainable System Solutions GmbH assessed four more buildings withing a supplementary study of the above mentioned study (Wyss et al. 2014). The focus of the study was to quantify the overall environmental impacts of high tech and low tech office buildings along with a high tech residential building. In parallel, the greenhouse gas emissions and the non-renewable primary energy demand caused by these activities are quantified. The results were then compared to the office and residential buildings analyzed in Wyss et al. (2014). This comparison reveals the reduction potential in environmental impacts due to improved building designs.

 

Summary of the study of Wyss et al. 2014:

The large Swiss construction activity causes a major share of the total environmental impact of our society. According to a recent study, about one fourth of all greenhouse gas emissions and about one fifth of the total environmental impact are caused by the housing and construction sector. Relevant reductions of environmental impacts could be gained in this area. In Switzerland valuable instruments are available, in which target and reference values of greenhouse gas emissions and primary energy demand (non renewable) for buildings are listed, namely the SIA bulletin 2040 SIA efficiency path for energy, the label Minergie-P-Eco and the standard sustainable construction Switzerland (SNBS). For a comprehensive building assessment, this study analyses whether a third indicator, besides the greenhouse gas emissions and the primary energy demand (non renewable), shall be introduced. It is of interest if the method of ecological scarcity can be used to assess the environmental performance of buildings.

On one hand, reference and target values of buildings in terms of the total environmental impact are assessed. On the other hand the additional benefit of this added indicator is evaluated. This study serves as a basis for recommendations if and how the SIA bulletin 2040 SIA efficiency path for energy and the section ‘environment’ of SNBS are complemented with the indicator total environmental impact. Life cycle assessments of 31 case studies are the groundwork for the evaluation.  

The life cycle modelling of the buildings is done accordingly to the methodology of the SIA bulletin 2040 SIA efficiency path for energy. The total environmental impact is displayed separately for the construction phase (construction, servicing and deconstruction), the use phase (room heating, hot water provision, ventilation, lighting and operational energy) as well as for the induced mobility. The impacts and emissions of the construction phase are evaluated according to standardized service life times of building components and a service life time of 60 years for the whole building (see SIA bulletin 2032). The reference value is defined as one square meter energy reference area and year. The total environmental impact is assessed with the method of ecological scarcity 2006. The database ecoinvent v2.2 and the KBOB-recommendation 2009/1:2012 serve as the basis.

In sensitivity analyses these databases are replaced by the current database ecoinvent v2.2+ and the KBOB-recommendation 2009/1:2014. In the sensitivity analysis the calculations are further performed with updated indicators (method of ecological scarcity 2013 and greenhouse gas emissions according to IPCC 2013). As additional sensitivities the materialization of the buildings and its impact on the environmental performance as well as variations for energy carriers for the room heating and hot water are assessed.

The target values for the total environmental impact of buildings are identified based on the present total environmental impact of the Swiss building pool and on the impact-reduction needed. In contrast to the greenhouse gas emissions and the primary energy demand (non renewable) which base on targets of the 2000-watt-society, no official goals and targets exist for the total environmental impact. As orientational values the environmental targets from the method of ecological scarcity based on the Swiss legislation are used.

The total environmental impact of the present building pool is 65’000, 57’000 and 109’000 eco-points/m²/a for residential buildings, schools and offices. Thereof the target values were derived: 29’000 eco-points/m²/a for residential buildings, 25’000 eco-points/m²/a for schools and 48’000 eco-points/m²/a for offices. The case studies show variations between 25’000 – 43’000 eco-points/m²/a within the residential buildings, 21’000 – 36’000 eco-points/m²/a within the schools and 40’000 – 45’000 eco-points/m²/a within the office buildings. Hence 13 of the 31 buildings analyzed lie below their target values. Five of these fulfill as well the requirements of greenhouse gas emissions and primary energy demand (non renewable). Fig. 1 shows the results of all buildings indexed to the target value (total environmental impacts).

 

Fig. 1          Total environmental impact of all buildings, displayed in construction, use stage and induced mobility, indexed (target value = 100 %)
*: Building below target value primary energy demand (non renewable) and greenhouse gas emissions
§: Building below target target value primary energy demand (non renewable)
#: Building below target target value greenhouse gas emissions

The specific environmental impacts of these buildings are often distinctly lower than the impact of the average Swiss building pool. Nevertheless it is feasible to define a target value for the total environmental impact of buildings which can be fulfilled by refurbished and newly constructed buildings. Compared to the indicators primary energy demand (non renewable) and greenhouse gas emissions the building’s infrastructure (ventilation, electric installation, etc.) gains importance when assessed with the method of ecological scarcity.

For most of the buildings analyzed the greenhouse gas emissions set the limiting factor. For these buildings an additional indicator is superfluous. Hence it is not necessary to extend the SIA bulletin 2040 SIA efficiency path for energy or the SNBS with a third indicator total environmental impact. The role of this indicator is not directive but consolidating. However valuable information can be gained by applying the total environmental impacts on buildings especially within the materialization and the choice of the building’s infrastructure.

It is recommended to assess the buildings greenhouse gas emissions and primary energy demand (non renewable) as a first step. As a second step the total environmental impact can be used to optimize the construction and use stage.